This is an observational research study whose purposes are to see the effects of repeated hyperbaric oxygen therapy treatments on the levels of stem/progenitor cells in peripheral circulating blood following five days of treatment, 90 minutes per day at 2.0 atmospheres absolute in 100% USP Grade Oxygen. Hyperbaric oxygen has a greater oxygen concentration than air at sea level. In this research, the concentration of oxygen will be twice the level of oxygen at sea level.